/Engine/Source/Runtime/Foliage/Public/InstancedFoliageActor.h
Perf Warnin: potentially slow! Dev-only use recommended. Returns list of meshes and counts for all nearby instances. OutCounts accumulates between runs.
void GetOverlappingMeshCounts ( const FSphere & Sphere, [TMap](API\Runtime\Core\Containers\TMap)< [UStaticMesh](API\Runtime\Engine\Engine\UStaticMesh) *, int32 > & OutCounts ) const